Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$130.52	9.506%	$142.9272	$142.93	$142.95	$142.90
Purchase #2	$222.46	4.231%	$231.8723	$231.87	$231.85	$231.90
Purchase #3	$83.94	6.769%	$89.6219	$89.62	$89.60	$89.60
Purchase #4	$41.56	13.415%	$47.1353	$47.14	$47.15	$47.10
Purchase #5	$62.94	8.557%	$68.3258	$68.33	$68.35	$68.30
Purchase #6	$73.88	9.496%	$80.8956	$80.90	$80.90	$80.90
Purchase #7	$191.76	13.837%	$218.2938	$218.29	$218.30	$218.30
7 purchase totals =	$807.06		$879.0719	$879.08	$879.10	$879.00